Displacement control mechanism of variable displacement type compressor

ABSTRACT

A displacement control mechanism controls displacement of a variable displacement type compressor that forms a refrigerant circulation circuit for an air conditioning apparatus. The displacement is decreased as a pressure in a crank chamber rises while being increased as the pressure in the crank chamber falls. The displacement control mechanism includes a bleed passage, a supply passage, a first control valve and a second control valve. The second control valve includes a back pressure chamber, a valve chamber, a valve body, a spring and a second valve portion. The second valve portion is provided with the back surface of the valve body. The second valve portion closes an opening of an introduction passage in the back pressure chamber when the first valve portion maximizes the opening of the bleed passage.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a displacement control mechanismfor controlling the displacement of a variable displacement typecompressor that forms a part of refrigerant circulation circuit of anair conditioning apparatus and the displacement of which is decreased asa pressure in a crank chamber of the compressor rises while beingincreased as the pressure in the crank chamber falls.

[0002] There is known a displacement control mechanism shown in FIG. 7,in which the pressure in a crank chamber 153 or crank pressure Pc isadjusted by technique, what is called, a supply control.

[0003] Namely, in a variable displacement type swash plate compressor(hereinafter the compressor), the crank chamber 153 communicates with asuction chamber 155 via a bleed passage 154. A discharge chamber 151 ofthe compressor communicates with the crank chamber 153 via a supplypassage 152 in which a control valve 156 is arranged. The amount ofrefrigerant gas introduced into the crank chamber 153 via the supplypassage 152 is controlled by adjusting the opening of the control valve156, and the crank pressure Pc is determined in accordance with therelation between the amounts of refrigerant gas introduced into andbleeding from the crank chamber 153.

[0004] A fixed throttle 158 is arranged in the bleed passage 154 so thatthe refrigerant gas bleeds slowly from the crank chamber 153 to thesuction chamber 155. Thus, even when the amount of the refrigerant gassupplied from the discharge chamber 151 to the crank chamber 153 via thesupply passage 152 is small, the crank pressure Pc is steadilyincreased. Therefore, when the control valve 156 increases the openingof the supply passage 152, the crank pressure Pc is rapidly increased.Consequently, appropriate response in decreasing the compressordisplacement is obtained.

[0005] Also, an amount of gas that blows from a cylinder bore 157 to thecrank chamber 153 and that leaks to the suction chamber 155 via thebleed passage 154, and an amount of the refrigerant gas that moves fromthe discharge chamber 151 to the suction chamber 155 via the crankchamber 153 as mentioned above, so-called, a kind of internal leakage,are reduced as much as possible by the provision of the fixed throttle158. Consequently, decrease in efficiency of the compressor caused byproviding the displacement control mechanism is prevented.

[0006] However, the arrangement of the fixed throttle 158 on the bleedpassage 154 makes decrease in a pressure in the crank chamber 153 slow.In other words, response in increasing the displacement of thecompressor deteriorates. Especially, when the compressor is started, thecrank pressure Pc tends to be excessively increased since the liquidrefrigerant accumulated in the crank chamber 153 evaporates and thefixed throttle 158 hampers smooth flow of the refrigerant gas from thecrank chamber 153. Therefore, even when the control valve 156 closes thesupply passage 152 so as to increase the displacement of the compressorin response to the requirement for cooling shortly after the compressoris started, it takes time before the displacement of the compressor isactually increased, and starting performance of an air conditioningapparatus deteriorates.

[0007] To solve such problems, it is proposed to provide a secondcontrol valve 161 for controlling the opening of the bleed passage 154in addition to the control valve (first control valve) 156, as shown inFIG. 8. Please see Japanese Unexamined Patent Publication No. 2002-21721(pages 7 to 10, and FIGS. 1, 4 and 5).

[0008] Specifically, in the proposed structure, a region K is providedin the supply passage 152 downstream of the position of the firstcontrol valve 156 (i.e. the position of the valve opening adjustment)and upstream of a fixed throttle 169, as shown in FIG. 8. The secondcontrol valve 161 is a spool type valve that includes a spool 162 and aback pressure chamber 166 into which the pressure in the region K isintroduced. A valve chamber 167 of the second control valve 161 forms apart of the bleed passage 154 and communicates with the suction chamber155. The valve chamber 167 also communicates with the crank chamber 153via a valve hole 168 that forms the upstream portion of the bleedpassage 154.

[0009] The spool 162 is movably fitted in a spool supporting recess 164that is formed in a compressor housing. The spool 162 includes a valveportion 162 a that is located in the valve chamber 167 and a backsurface 162 b that is located in the back pressure chamber 166. Thespool 162 or the valve portion 162 a is positioned by various forcesapplied thereto such as urging force of the pressure in the backpressure chamber 166 acting on the back surface 162 b in the directionto close the valve, urging force of a spring 165 acting in the valveopening direction and force of the crank pressure Pc that is applied inthe valve opening direction.

[0010] When the first control valve 156 closes the supply passage 152, apressure PdK in the back pressure chamber 166 of the second controlvalve 161 becomes substantially the same as the crank pressure Pc and,therefore, the spool 162 of the second control valve 161 is positionedby the spring 165 where the opening of the valve hole 168 is maximum.When the bleed passage 154 is widely opened by the second control valve161, flowing of the refrigerant from the crank chamber 153 to thesuction chamber 155 is prompted. Therefore, when the first control valve156 closes the supply passage 152 so as to increase the displacement ofthe compressor shortly after the compressor is started, the displacementof the compressor is immediately increased, so that the startingperformance of the air conditioning apparatus is improved.

[0011] A spring having a small urging force is utilized as the urgingspring 165. Thus, when the supply passage 152 is opened even slightly bythe first control valve 156 and the pressure PdK in the region K exceedsthe crank pressure Pc, the spool 162 moves against the urging spring165, and the valve portion 162 a minimizes the opening of the valve hole168 that is not zero. Therefore, when the valve hole 168 is thus set atthe minimum opening that is not zero, the second control valve 161functions similarly to the above-described fixed throttle 158 shown inFIG. 7, and the decrease in the efficiency of the compressor caused byproviding the displacement control mechanism is prevented.

[0012] However, the first control valve 156 leaks the refrigerant gas byperformance deterioration due to aged deterioration even in a state thatthe first control valve 156 closes the supply passage 152. Thus, thepressure Pdk in the back pressure chamber 166 of the second controlvalve 161 rises due to the refrigerant gas which leaks from the firstcontrol valve 156, and the second control valve 161 may inappropriatelyset the opening of the bleed passage 154 at the minimum opening.Therefore, the refrigerant gas is flowed slowly from the crank chamber153 to the suction chamber 155 through the bleed passage 154, and thestarting performance of the air conditioning apparatus is insufficient.

[0013] To solve such a problem, a spring having large urging force isadopted as the urging spring 165 so that the spool 162 or the valveportion 162 a maintains the maximum opening of the valve hole 168 evenif the pressure Pdk in the back pressure chamber 166 is raised somewhat.

[0014] However, when the spring having large urging force is adopted asthe urging spring 165, the second control valve 161 cannot set the bleedpassage 154 at the minimum opening unless the first control valve 156widely opens the supply passage 152 and the pressure Pdk in the backpressure chamber 166 is greatly raised. Therefore, in a state that thefirst control valve 156 opens the supply passage 152, such period thatthe second control valve 161 sets the bleed passage 154 at an openingother than the minimum opening, in other words, such period that thesecond control valve 161 cannot function similarly to the fixed throttle158 increases, and decrease in the efficiency of the compressor iscaused.

SUMMARY OF THE INVENTION

[0015] The present invention is directed to a displacement controlmechanism that prevents a second control valve from inappropriatelyoperating even when performance of a first control valve deteriorateswhile preventing decrease in efficiency of a variable displacement typecompressor.

[0016] According to the present invention, a displacement controlmechanism controls displacement of a variable displacement typecompressor that forms a refrigerant circulation circuit for an airconditioning apparatus. The displacement is decreased as a pressure in acrank chamber rises while being increased as the pressure in the crankchamber falls. The refrigerant circulation circuit has a suctionpressure region and a discharge pressure region. The displacementcontrol mechanism includes a bleed passage, a supply passage, a firstcontrol valve and a second control valve. The bleed passageinterconnects the crank chamber with the suction pressure region. Thesupply passage interconnects the crank chamber with the dischargepressure region. The first control valve is located on the supplypassage for adjusting an opening of the supply passage at a position ofvalve opening adjustment. The second control valve includes a backpressure chamber, a valve chamber, a valve body, a spring and a secondvalve portion. A pressure on a downstream side of the position of valveopening adjustment of the first control valve in the supply passage isintroduced to the back pressure chamber through an introduction passage.The valve chamber forms a part of the bleed passage. The valve body hasa first valve portion located in the valve chamber and a back surfacelocated in the back pressure chamber. The first valve portion decreasesan opening of the bleed passage as a pressure in the back pressurechamber which is applied to the back surface rises. The spring urges thevalve body so that the first valve portion increases the opening of thebleed passage. The second valve portion is provided with the backsurface of the valve body. The second valve portion closes an opening ofthe introduction passage in the back pressure chamber when the firstvalve portion maximizes the opening of the bleed passage.

[0017] Other aspects and advantages of the invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The features of the present invention that are believed to benovel are set forth with particularity in the appended claims. Theinvention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

[0019]FIG. 1 is a longitudinal sectional view illustrating a variabledisplacement type swash plate compressor;

[0020]FIG. 2 is a longitudinal sectional view illustrating a firstcontrol valve;

[0021]FIG. 3 is a partially enlarged view illustrating a second controlvalve and its vicinity of FIG. 1;

[0022]FIG. 4 is a longitudinal sectional view illustrating operation ofthe second control valve;

[0023]FIG. 5 is an enlarged longitudinal sectional view illustratinganother second control valve and its vicinity;

[0024]FIG. 6 is an enlarged longitudinal sectional view illustrating yetanother second control valve and its vicinity;

[0025]FIG. 7 is a schematic view illustrating a prior art displacementcontrol mechanism; and

[0026]FIG. 8 is a longitudinal sectional view illustrating a prior artsecond control valve and its vicinity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The following will describe a preferred embodiment of the presentinvention. In the preferred embodiment, the present invention is appliedto a variable displacement type swash plate compressor (hereinafter thecompressor) that is used in a vehicle air conditioning apparatus forcompressing refrigerant gas.

[0028] Referring to FIG. 1, the compressor includes a cylinder block 11,a front housing 12, a valve plate assembly 13 and a rear housing 14. InFIG. 1, the left side and the right side respectively correspond to thefront side and the rear side of the compressor. The front housing 12 isfixedly joined to the front end of the cylinder block 11, and the rearhousing 14 is fixedly joined to the rear end of the cylinder block 11via the valve plate assembly 13. The cylinder block 11, the fronthousing 12 and the rear housing 14 cooperate to form a compressorhousing.

[0029] A crank chamber 15 is defined by the cylinder block 11 and thefront housing 12. A drive shaft 16 is rotatably supported in the crankchamber 15. A lug plate 17 is fixed to the drive shaft 16 so as to beintegrally rotated with the drive shaft.

[0030] The front end of the drive shaft 16 is operatively connected to avehicle engine E as an external drive source via a power transmissionmechanism PT. The power transmission mechanism PT may be a clutchmechanism (e.g. an electromagnetic clutch) that selectively transmitsand blocks driving power according to electric control from an externaldevice, or a continuous transmission type clutchless mechanism (e.g. thecombination of a belt and a pulley) that dispenses with the above clutchmechanism. In the present preferred embodiment, the clutchless typepower transmission mechanism PT is utilized.

[0031] A swash plate 18 as a cam plate is accommodated in the crankchamber 15. The swash plate 18 is slidably and inclinably supported bythe drive shaft 16. A hinge mechanism 19 is interposed between the lugplate 17 and the swash plate 18. Thus, a hinge connection between thelug plate 17 and the swash plate 18 via the hinge mechanism 19 and thesupport of the swash plate 18 by the drive shaft 16 allow the swashplate 18 to rotate synchronously with the lug plate 17 and the driveshaft 16 as well as to incline with respect to an axis of the driveshaft 16 in accordance with the sliding movement of the swash plate 18in the axial direction of the drive shaft 16.

[0032] A plurality of cylinder bores 11 a is formed in the cylinderblock 11 extending axially through the cylinder block 11 and is arrangedaround the drive shaft 16. In FIG. 1, only one cylinder bore is shown. Asingle-head piston 20 is accommodated in each of the cylinder bores 11 afor reciprocation therein. The front and rear openings of the cylinderbores 11 a are respectively closed by the pistons 20 and the valve plateassembly 13. Compression chambers are defined in the cylinder bores 11a, and the volumes of the compression chambers are varied in accordancewith the reciprocating movement of the pistons 20. Each of the pistons20 is engaged with the periphery of the swash plate 18 via a pair ofshoes 10, so that the rotation of the swash plate 18 with the driveshaft 6 is converted into linear reciprocating movement of the pistons20.

[0033] A suction chamber 21 and a discharge chamber 22 are definedbetween the valve plate assembly 13 and the rear housing 14. The suctionchamber 21 is located in the middle region of the rear housing 14 and issurrounded by the discharge chamber 22. A suction port 23 and a suctionvalve 24 are formed in the valve plate assembly 13 for each of thecylinder bores 11 a. The suction valve 24 is adapted to open and closethe suction port 23. A discharge port 25 and a discharge valve 26 arealso formed in the valve plate assembly 13 for each of the cylinderbores 11 a. The suction chamber 21 communicates with each of thecylinder bores 11 a via the corresponding suction port 23, and each ofthe cylinder bores 11 a communicates with the discharge chamber 22 viathe corresponding discharge port 25.

[0034] As each of the pistons 20 moves from the top dead center towardthe bottom dead center, the refrigerant gas is drawn into thecorresponding cylinder bore 11 a via the associated suction port 23pushing away the associated suction valve 24. As the pistons 20 movefrom the bottom dead center toward the top dead center, the refrigerantgas introduced into the cylinder bore 11 a is compressed to apredetermined pressure and is discharged into the discharge chamber 22via the associated discharge port 25 pushing away the discharge valve26.

[0035] An inclination angle of the swash pate 18, which is defined as anangle made between the swash plate 18 and a plane perpendicular to theaxis of the drive shaft 16 is varied in accordance with the pressure inthe crank chamber 5 (or a crank pressure Pc) between the minimuminclination angle as indicated by a solid line in FIG. 1 and the maximuminclination angle as indicated by a two-dot chain line in FIG. 1.

[0036] A displacement control mechanism for controlling the crankpressure Pc which has bearing on control of the inclination angle of theswash plate 18 includes a first bleed passage 27, a second bleed passage28, a supply passage 29, a first control valve CV1 and a second controlvalve CV2.

[0037] The first and second bleed passages 27 and 28 interconnect thecrank chamber 15 with the suction chamber 21 as a suction pressure (Ps)region. The second bleed passage 28 has a fixed throttle 28 a andextends through the cylinder block 11 and the valve plate assembly 13.The supply passage 29 interconnects the discharge chamber 22 as adischarge pressure (Pd) region with the crank chamber 15. The firstcontrol valve CV1 is arranged in the supply passage 29 for adjusting theopening of the supply passage 29. It is noted that the first bleedpassage 27 and the supply passage 29 are partially shared therebetweenas will be later described.

[0038] The first control valve CV1 adjusts the opening of the supplypassage 29 while the second control valve CV2 adjusts the opening of thesupply passage 29 and the first bleed passage 27. By so doing, thebalance between [an] the amount of high-pressure discharge gasintroduced from the discharge chamber 22 into the crank chamber 5 viathe supply passage 29 and [an] the amount of the refrigerant gas flowingfrom the crank chamber 5 into the suction chamber 21 via the first andsecond bleed passages 27 and 28 is controlled, and the crank pressure Pcis determined, accordingly. Pressure difference between the crankpressure Pc and the internal pressure in the cylinder bores 11 a via thepistons 20 is changed in accordance with the variation of the crankpressure Pc, and the inclination angle of the swash plate 12 is varied,accordingly. Consequently, the stroke of pistons 20, that is, thedisplacement of the compressor is adjusted.

[0039] For example, when the first control valve CV1 reduces the openingof the supply passage 29 and the crank pressure Pc is decreased, theinclination angle of the swash plate 18 is increased, and thedisplacement of the compressor is increased. On the other hand, when thefirst control valve CV1 increases the opening of the supply passage 29and the crank pressure Pc is increased, the inclination angle of theswash plate 18 is decreased, and the displacement of the compressor isdecreased. It is note that the minimum displacement of the compressor isset at zero or about zero

[0040] A refrigerant circulation circuit (or a refrigeration cycle) ofthe vehicle air conditioning apparatus includes the above-describedcompressor and an external refrigerant circuit 30. The externalrefrigerant circuit 30 includes a condenser 31, an expansion valve 32and an evaporator 33. A circulation pipe 35 for the refrigerant isprovided on the downstream side of the external refrigerant circuit 30,interconnecting the outlet of the evaporator 33 with the suction chamber21 of the compressor. A circulation pipe 36 for the refrigerant isprovided on the upstream side of the external refrigerant circuit 30,interconnecting the discharge chamber 22 of the compressor with theinlet of the condenser 31. The compressor draws and compresses thereinthe refrigerant gas which is introduced from the downstream side of theexternal refrigerant circuit 30 into the suction chamber 21, and thendischarges the compressed refrigerant gas to the discharge chamber 22which interconnects with the upstream side of the external refrigerantcircuit 30.

[0041] As shown in FIG. 2, the first control valve CV1 includes a valveportion in the upper half thereof as seen on the drawing of FIG. 2 and asolenoid portion 60 in the lower half. The valve portion adjusts theopening (a degree of throttle) of the supply passage 29 thatinterconnects the discharge chamber 22 with the crank chamber 15. Thesolenoid portion 60 is an actuator for controlling the operation of avalve rod 40 arranged in the control valve CV1 in response to a controlsignal from an external device. The valve rod 40 is a rod-like memberwhich includes a partition portion 41 at the top of the rod, aconnection portion 42, a valve body portion 43 at the middle and a guiderod portion 44 at the base.

[0042] A valve housing 45 for the first control valve CV1 includes avalve body housing 45 a forming its upper part and an actuator housing45 b [in] forming its lower part. A valve accommodating chamber 46, acommunication passage 47 and a pressure sensing chamber 48 are definedin the valve body housing 45 a. The valve rod 40 is arranged in thevalve accommodating chamber 46 and the communication passage 47 foraxial movement, that is, movement in the vertical direction [of] as seenin FIG. 2. The partition portion 41 of the valve rod 40 is inserted[into] through the communication passage 47 thereby to shut off thecommunication between the pressure sensing chamber 48 [from] and thecommunication passage 47.

[0043] Ports 51 and 52 are formed through the peripheral wall of thevalve body housing 45 a. The port 51 communicates with the valveaccommodating chamber 46, and the port 52 communicates with thecommunication passage 47, respectively. The valve accommodating chamber46 communicates with the discharge chamber 22 of the compressor via theport 51 and the upstream part of the supply passage 29, or a passage 84.The communication passage 47 communicates with the crank chamber 15 ofthe compressor via the port 52, the downstream part of the supplypassage 29 or a passage 83, the second control valve CV2 and a passage75. The supply passage 29 includes the passage 84, the port 51, thevalve accommodating chamber 46, the communication passage 47, the port52, the passage 83, the second control valve CV2 and the passage 75.

[0044] The valve body portion 43 of the valve rod 40 is located in thevalve accommodating chamber 46. A valve seat 53 is formed at the steppedportion located between the valve accommodating chamber 46 and thecommunication passage 47, and the communication passage 47 functions asa valve hole. When the valve rod 40 moves upward from the position ofFIG. 2, where the communication passage 47 (or the supply passage 29) isopened, to a position where the valve body portion 43 contacts the valveseat 53, the communication passage 47 (the supply passage 29) is closed.

[0045] A bellows 50 is accommodated in the pressure sensing chamber 48.The upper end of the bellows 50 is fixed to the valve housing 45. Thetop of the partition portion 41 of the valve rod 40 is fitted into thelower end of the bellows 50. The pressure sensing chamber 48 is dividedinto two chambers by the bellows 50, namely a first pressure chamber 54formed inside the bellows and a second pressure chamber 55 formedoutside the bellows 50.

[0046] As shown in FIG. 1, a throttle 36 a is formed on the circulationpipe 36 between the discharge chamber 22 and the external refrigerantcircuit 30. Referring back to FIG. 2, the first pressure chamber 54communicates via a first pressure introducing passage 37 with thedischarge chamber 22 at a first pressure monitoring point P1 that islocated on the upstream side of the throttle 36 a. The second pressurechamber 55 communicates via a second pressure introducing passage 38with the circulation pipe 36 at a second pressure monitoring point P2that is located on the downstream side of the throttle 36 a. Thus, amonitored pressure PdH at the first pressure monitoring point P1 isintroduced into the first pressure chamber 54, and a monitored pressurePdL at the second pressure monitoring point P2 is introduced into thesecond pressure chamber 55.

[0047] The lower end of the bellows 50 vertically moves in accordancewith the pressure difference (PdH−PdL) between the pressures on oppositesides of the throttle 36 a. Thus, the position of the valve rod 40 (orthe valve body portion 43) is determined by varying the pressuredifference. The pressure difference (PdH−PdL) between the pressures onopposite sides of the throttle 36 a varies depending on the refrigerantflow rate in the refrigerant circulation circuit. For example, when therefrigerant flow rate is increased, the pressure difference (PdH−PdL) isincreased. On the other hand, when the refrigerant flow rate isdecreased, the pressure difference (PdH−PdL) is decreased. The bellows50 operates the valve body portion 43 such that the displacement of thecompressor is changed so as to cancel the variation of the pressuredifference (PdH−PdL)

[0048] The solenoid portion 60 of the first control valve CV1 has in themiddle of the actuator housing 45 b an accommodating cylinder 61 thathas a cylindrical shape with a bottom. A fixed core 62 of a column shapeis fittingly fixed to the upper opening of the accommodating cylinder61. Thus, a solenoid chamber 63 is defined in the lower portion of theaccommodating cylinder 61.

[0049] A movable core 64 is axially movably accommodated in the solenoidchamber 63. A guide hole 65 extends through the center of the fixed core62 in the axial direction of the valve rod 40. The guide rod portion 44of the valve rod 40 is arranged in the guide hole 65 so as to move inthe axial direction of the valve rod 40. The guide rod portion 44 isfittingly fixed to the movable core 64 of the solenoid chamber 63. Thus,the movable core 64 and the valve rod 40 vertically move together.

[0050] A helical spring 66 is accommodated between the fixed core 62 andthe movable core 64 in the solenoid chamber 63 for urging the valve rod40 in such direction that causes the valve body portion 43 to move awayfrom the valve seat 53.

[0051] A coil 67 is wound around the outer periphery of theaccommodating cylinder 61 over a range covering the fixed core 62 andthe movable core 64. Driving signal is transmitted from a drivingcircuit 68 a to the coil 67, based on the command from a control device68 in accordance with air conditioning load. With such driving signaltransmitted to the coil 67, electromagnetic force (or electromagneticattraction) is generated between the fixed core 62 and the movable core64, the magnitude of which electromagnetic force is determined by amountof electric power supplied to the coil 67. The electromagnetic force istransmitted to the valve rod 40 (or the valve body portion 43) throughthe movable core 64. Controlling energization of the coil 67 isperformed by adjusting the voltage applied to the coil 67, and dutycycle control is utilized in the present preferred embodiment.

[0052] The solenoid portion 60 of the first control valve CV1 varies theelectromagnetic force for application to the valve body portion 43 inaccordance with the amount of the electric power supplied from anexternal device. In the first control valve CV1, therefore, controltarget (or set pressure difference) for the pressure difference(PdH−PdL) between the pressures on opposite sides of the throttle 36 a,that is, a standard for positioning the valve body portion 43 by thebellows 50 is changed by varying the electromagnetic force forapplication to the valve body portion 43. In other words, the firstcontrol valve CV1 is formed to internally autonomously position thevalve rod 40 (or the valve body portion 43) in accordance with thevariation of the pressure difference (PdH−PdL) between the first andsecond pressure monitoring points P1 and P2 such that the set pressuredifference determined by the amount of the electric power supplied tothe coil 67 is maintained.

[0053] The set pressure difference of the first control valve CV1 isvaried by adjusting the amount of the electric power supplied to thecoil 67 from the external device. For example, when the duty ratio thatis commanded from the control device 68 to the driving circuit 68a isincreased, electromagnetic urging force of the solenoid portion 60 isincreased, and the set pressure difference of the first control valveCV1 is increased, accordingly. With the set pressure difference of thefirst control valve CV1 thus increased, the displacement of thecompressor is increased. On the other hand, when the duty ratio that iscommanded from the control device 68 to the driving circuit 68 a isdecreased, electromagnetic urging force of the solenoid portion 60 isdecreased, and the set pressure difference of the first control valveCV1 is decreased. When the set pressure difference of the first controlvalve CV1 is decreased, the displacement of the compressor is decreased.

[0054] It is noted that the compressor of the present preferredembodiment is what is called a clutchless type compressor, and the driveshaft 16 is continuously rotated while the engine E is driven. When theair conditioning is not needed, however, supplying the electric power tothe coil 67 is stopped by switching off the air conditioning apparatus,that is, the duty ratio is zero, and the swash plate is set at theminimum inclination angle. Thus, the displacement of the compressor isset at the minimum displacement, namely, zero or about zero by only onemeaning. Therefore, even when the drive shaft 16 is rotated, supplyingthe refrigerant from the compressor to the external refrigerant circuit30 is substantially stopped, and the refrigeration cycle is stopped.

[0055] As shown in FIGS. 1, 3 and 4, an accommodation hole 70 is formedin a rear end surface of the rear housing 4 for accommodating thereinthe second control valve CV2. A valve housing 71 is fittingly fixed tothe accommodation hole 70. The valve housing 71 includes a cylindricalportion 72 whose outside diameter is smaller than that of theaccommodation hole 70 and a fitting portion 73 that continues from thecylindrical portion 72 on the opening side of accommodation hole 70 andis fittingly fixed to the accommodation hole 70. The valve housing 71 ispushed into the accommodation hole 70 such that the distal end of thecylindrical portion 72 contacts an inner bottom surface 70 a of theaccommodation hole 70.

[0056] The cylindrical portion 72, the end surface 73 a of the fittingportion 73 that faces the inside of the cylindrical portion 72, and theinner bottom surface 70 a of the accommodation hole 70 define anaccommodation chamber 74 in the cylindrical portion 72. A communicationspace 79 is formed between the outer peripheral surface of thecylindrical portion 72 and the inner peripheral surface of theaccommodation hole 70. The communication space 79 communicates with thecrank chamber 15 via a passage 75 arranged on the side of the crankchamber 15.

[0057] In the accommodation chamber 74, a spool 76 that serves as avalve body is movably accommodated in the direction in which thecylindrical portion 72 extends. The spool 76 is slidable between theposition at which the spool 76 contacts the inner bottom surface 70 a ofthe accommodation hole 70 and the position at which the spool 76contacts the end surface 73 a of the fitting portion 73, and has acylindrical shape with a bottom on the side of the end surface 73 a ofthe fitting portion 73.

[0058] The spool 76 divides the accommodation chamber 74 into front andrear spaces, which are blocked by the contact between the outerperipheral surface of the spool 76 and the inner peripheral surface ofthe accommodation chamber 74. The blocked front and rear spaces arerespectively defined as a valve chamber 77 on the side of the innerbottom surface 70 a of the accommodation hole 70 and a back pressurechamber 78 on the side of the end surface 73 a of the fitting portion73. In the spool 76, the end surface on the opening side of the spool 76arranged in the valve chamber 77 is defined as an end valve portion 76 aand the outer bottom surface of the spool 76 arranged in the backpressure chamber 78 is defined as a back surface 80. The spool 76contacts the inner bottom surface 70 a of the accommodation hole 70 withthe end valve portion 76 a.

[0059] The cylindrical portion 72 of the valve housing 71 forms a firstgap-hole 72 a and a second gap-hole 72 b therethrough. The firstgap-hole 72 a communicates with the inside and the outside of thecylindrical portion 72. The second gap-hole 72 b is located nearer thefitting portion 73 than the first gap-hole 72 a, and communicates withthe inside and the outside of the cylindrical portion 72.

[0060] The first gap-hole 72 a communicates with the valve chamber 77and the communication space 79 in a state that the spool 76 is incontact with the end surface 73 a of the fitting portion 73 as shown inFIG. 4. The first gap-hole 72 a is blocked by a region on the side ofthe valve chamber 77 in the outer peripheral surface of the spool 76,that is, a first peripheral valve portion 76 b in a state that the spool76 is in contact with the inner bottom surface 70 a of the accommodationhole 70. Thus, the communication between the valve chamber 77 and thecommunication space 79 is blocked as shown in FIG. 3.

[0061] The second gap-hole 72 b communicates with the back pressurechamber 78 and the communication space 79 in a state that the spool 76is in contact with the inner bottom surface 70 a of the accommodationhole 70 as shown in FIG. 3. The second gap-hole 72 b is blocked by aregion on the side of the back pressure chamber 78 in the outerperipheral surface of the spool 76, that is, a second peripheral valveportion 76 c in a state that the spool 76 is in contact with the endsurface 73 a of the fitting portion 73. Thus, the communication betweenthe back pressure chamber 78 and the communication space 79 is blockedas shown in FIG. 4.

[0062] The valve chamber 77 communicates with the suction chamber 21 viaa passage 81 formed in the rear housing 14. The passage 81 is openedmore inwardly than an annular region or a sealed region in which the endvalve portion 76 a of the spool 76 contacts the inner bottom surface 70a of the accommodation hole 70.

[0063] Therefore, the communication of the inside and the outside of thevalve chamber 77 relative to the sealed region of the end valve portion76 a are blocked in a state that the spool 76 is in contact with theinner bottom surface 70 a of the accommodation hole 70. In addition, thefirst gap-hole 72 a is blocked by the first peripheral valve portion 76b. Thus, the communication between the passage 81 and the communicationspace 79 (or the passage 75) is blocked as shown in FIG. 3. Thecommunication of the inside and the outside of the valve chamber 77relative to the sealed region of the end valve portion 76 a are openedin a state that the spool 76 is in contact with the end surface 73 a ofthe fitting portion 73. In addition, the first gap-hole 72 a is openedby the first peripheral valve portion 76 b of the spool 76. Thus, thecommunication between the passage 81 and the communication space 79 (orthe passage 75) is opened as shown in FIG. 4.

[0064] In the present preferred embodiment, the passage 81, the valvechamber 77, the first gap-hole 72 a, the communication space 79, and thepassage 75 which is shared with the supply passage 29 form the firstbleed passage 27. Therefore, in the spool 76, the end valve portion 76 aand the first peripheral valve portion 76 b which open and close thecommunication between the passage 81 and the communication space 79 areregarded as a first valve portion for adjusting the opening of the firstbleed passage 27.

[0065] The back pressure chamber 78 communicates with the port 52 of thefirst control valve CV1 via a passage 82 formed in the fitting portion73 of the valve housing 71 and a passage 83 that forms the supplypassage 29. The passage 82 is opened at an opening 82 a formed at thecenter of the end surface 73 a of the fitting portion 73 in the backpressure chamber 78. Therefore, the refrigerant gas flowed from thedischarge chamber 22 is introduced into the back pressure chamber 78 viaa passage 84, the first control valve CV1 which is in a opening state,the passages 83 and 82. That is, a pressure Pdk on the downstream sideof the position of the valve opening adjustment of the first controlvalve CV1, or the valve seat portion 53, in the supply passage 29 isapplied to the back pressure chamber 78 via the passage 82 that servesas an introduction passage.

[0066] The refrigerant gas introduced from the discharge chamber 22 tothe back pressure chamber 78 is flowed into the crank chamber 15 via thesecond gap-hole 72 b, the communication space 79 and the passage 75.That is, in the second control valve CV2, the passage 82, the backpressure chamber 78, the second gap-hole 72 b and the communicationspace 79 form the supply passage 29.

[0067] The spool 76 is urged toward the inner bottom surface 70 a of theaccommodation hole 70, that is, in such direction that the end valveportion 76 a and the first peripheral valve portion 76 b of the firstvalve portion decrease the opening of the first bleed passage 27 by theforce of the pressure Pdk in the back pressure chamber 78 applied to theback surface 80. On the other hand, the spool 76 is urged toward the endsurface 73 a of the fitting portion 73, that is, in such direction thatthe end valve portion 76 a and the first peripheral valve portion 76 bof the first valve portion increase the opening of the first bleedpassage 27 by the force of the suction pressure Ps which is applied tothe end valve portion 76 a and the valve chamber 77.

[0068] A helical spring 85 is arranged in the spool 76 of the valvechamber 77. The spring 85 has a movable end and a fixed end on theopposite sides thereof. The movable end of the spring 85 is in contactwith the spool 76 while the fixed end of the spring 85 is held andaccommodated in an accommodating groove 70 b formed in the inner bottomsurface 70 a of the accommodation hole 70. The spring 85 urges the spool76 in such direction that the end valve portion 76 a and the firstperipheral valve portion 76 b of the first valve portion increase theopening of the first bleed passage 27.

[0069] That is, the spool 76 is positioned by the balance between theurging force in the valve closing direction of the end valve portion 76a and the first peripheral valve portion 76 b of the first valve portioncaused by the force of the pressure Pdk in the back pressure chamber 78,the urging force in the valve opening direction of the end valve portion76 a and the first peripheral valve portion 76 b of the first valveportion caused by the force of the pressure Ps in the valve chamber 77,and the urging force in the valve opening direction of the end valveportion 76 a and the first peripheral valve portion 76 b of the firstvalve portion caused by the force of the urging force 85.

[0070] Meanwhile, in the present embodiment, the back surface 80 of thespool 76 forms thereon a second valve portion 86 for opening and closingthe opening 82 a of the passage 82 in the back pressure chamber 78 inaccordance with the position of the spool 76. The second valve portion86 protrudes from the center of the back surface 80 of the spool 76 soas to face the opening 82 a of the passage 82. The second valve portion86 is shaped into a circular shape in a transverse section, and istapered so that the distal end of the second valve portion 86 becomes aminor diameter. The taper shape of the second valve portion 86 is suchshaped that the diameter of the proximal end thereof becomes larger thanthat of the opening 82 a of the passage 82 and the diameter of thedistal end thereof becomes smaller than that of the opening 82 a. Thesecond valve portion 86 is made of resilient material such as syntheticrubber or synthetic resin.

[0071] As shown in FIG. 4, the movement of the spool 76 toward thefitting portion 73 is regulated by the contact of the second valveportion 86 with the end surface 73 a of the fitting portion 73. In sucha state that the movement of the spool 76 is regulated by the contactwith the end surface 73 a of the fitting portion 73, that is, in a statethat the first bleed passage 27 is fully opened by the end valve portion76 a and the first peripheral valve portion 76 b of the first valveportion, the distal end of the second valve portion 86 enters the insideof the passage 82 via the opening 82 a while a taper surface 86 a of thesecond valve portion 86 contacts at an annular region on the rim of theopening 82 a of the passage 82. Thus, the communication between the backpressure chamber 78 and the passage 82 is blocked. In addition, in sucha state, the second gap-hole 72 b is blocked by the second peripheralvalve portion 76 c of the spool 76. Thus, the communication between thepassage 83 and the communication space 79 (or the passage 75) isblocked.

[0072] In contrast, as shown in FIG. 3, in a state that the movement ofthe spool 76 is regulated by the contact with the inner bottom surface70 a of the accommodation hole 70, that is, in a state that the firstbleed passage 27 is fully closed by the end valve portion 76 a and thefirst peripheral valve portion 76 b of the first valve portion, thesecond valve portion 86 is distanced from the end surface 73 a of thefitting portion 73 and the opening 82 a of the passage 82 is opened. Inaddition, in such a state, the second gap-hole 72 b is opened by thesecond peripheral valve portion 76 c of the spool 76. Thus, the passage83 and the communication space 79 (or the passage 75) are interconnectedwith each other.

[0073] The operating characteristics of the control valve CV2 will benow described. As shown in FIG. 3, in a state that the end valve portion76 a and the first peripheral valve portion 76 b of the first valveportion of the spool 76 of the second control valve CV2 have decreasedthe opening of the first bleed passage 27 from the fully opening stateof the first bleed passage 27, the second valve portion 86 of the spool76 opens the division of the back pressure chamber 78 and the passage 82and the pressure Pdk in the passage 82 is applied to the back pressurechamber 78. Therefore, in the second control valve CV2, if the crosssectional area of the back pressure chamber 78 that is perpendicular tothe axial direction of the spool 76 is represented as “SA”, and theurging force of the spring 85 is represented as “f”, conditionexpression (1) for increasing the opening of the first bleed passage 27in the second control valve CV2 is expressed as follows:

(Pdk−Ps)·SA<f  (1)

[0074] As shown in FIG. 4, in the second control valve CV2, in a statethat that the first bleed passage 27 is fully opened by the end valveportion 76 a and the first peripheral valve portion 76 b of the firstvalve portion of the spool 76, the second valve portion 86 of the spool76 blocks the communication between the back pressure chamber 78 and thepassage 82. Thus, the pressure Pdk in the passage 82 is not applied tothe back pressure chamber 78. Therefore, the pressure Pdk in the passage82 is applied only to the second valve portion 86 of the back surface 80of the spool 76. If the cross sectional area at the opening 82 a of thepassage 82 that is perpendicular to the axial direction of the passage82 is represented as “SB” (<“SA”), condition expression for decreasingthe opening of the first bleed passage 27 in the second control valveCV2 in a state that the first bleed passage 27 is fully opened isexpressed as follows:

(Pdk−Ps)·SB>f  (2)

[0075] When time has passed for more than a predetermined time after thevehicle engine E was stopped, the pressure in the refrigerantcirculation circuit is equalized at a relatively small value, and thusthe pressure Pdk and the suction pressure Ps equalized to each other.Since the condition expression (1) is effective and the conditionexpression (2) is not effective, as shown in FIG. 4, the spool 76 movesby the spring 85 and the second valve portion 86 blocks the supplypassage 29. At the same time, the end valve portion 76 a and the firstperipheral valve portion 76 b of the first valve portion fully opens thefirst bleed passage 27.

[0076] In a conventional compressor for a vehicle air-conditioningapparatus, any liquid refrigerant existing on the low pressure side ofthe external refrigerant circuit 30 with the vehicle engine E kept at astop for a long time flows into the crank chamber 15 via the suctionchamber 21 due to the fluid communication between the crank chamber 15and the suction chamber 21 via the first and second bleed passages 27and 28. Especially, when the temperature in the engine room where thecompressor is located is lower than that in the vehicle interior, alarge amount of the liquid refrigerant flows into the crank chamber 15via the suction chamber 21 and is accumulated in the crank chamber 15.

[0077] Therefore, when the vehicle engine E is started and thecompressor is also started thereby through the clutchless type powertransmission mechanism PT, the liquid refrigerant evaporates under theinfluence of heat generated by the vehicle engine E and also of thestirring effect of the swash plate 18, with the result that the crankpressure Pc tends to be increased regardless the opening of the firstcontrol valve CV1.

[0078] For example, when the vehicle engine E is started while thevehicle interior is hot, the control device 68 is operated in responseto the demand from an occupant to command maximum duty ratio to thedrive circuit 68 a, and the set pressure difference of the first controlvalve CV1 is set at the maximum value, accordingly, for performingcooling as required from the occupant. For this purpose, the firstcontrol valve CV1 closes the supply passage 29, and no high pressurerefrigerant gas is supplied from the discharge chamber 22 to the backpressure chamber 78 of the second control valve CV2 and the crankchamber 15. Therefore, even if evaporation of the liquid refrigerantoccurs in the crank chamber 15, the state wherein the pressuredifference between the crank pressure Pc and the suction pressure Psdoes not exceed the urging force f, that is, the state wherein thecondition expression (2) is not effective, continues.

[0079] Consequently, the spool 76 of the second control valve CV2 ismaintained by the urging force f of the spring 85 in such a state thatthe end valve portion 76 a and the first peripheral valve portion 76 bof the first valve portion fully opens the first bleed passage 27, andthe liquid refrigerant in the crank chamber 15, as well as therefrigerant gas evaporated from part of the liquid refrigerant, areimmediately flowed into the suction chamber 21 via the fully-openedfirst bleed passage 27. Thus, the crank pressure Pc is maintained at alow value since the first control valve CV1 closes the supply passage29, and the compressor increases the inclination angle of the swashplate 18 thereby to increase the displacement of the compressor to itsmaximum.

[0080] If the first control valve CV1 still closes the supply passage 29even after the liquid refrigerant is flowed out of the crank chamber 15,the first bleed passage 27 is fully opened by the end valve portion 76 aand the first peripheral valve portion 76 b of the first valve portionof the second control valve CV2 as described above. Thus, even if theamount of blow-by gas from the cylinder bores 11 a to the crank chamber15 is increased from the amount initially designed, the blow-by gas isimmediately flowed into the suction chamber 21 via the first and secondbleed passages 27 and 28. Therefore, the crank pressure Pc is maintainedat substantially the same level as the suction pressure Ps, and themaximum inclination angle of the swash plate 18, that is, the maximumdisplacement operation (100% displacement operation) of the compressoris maintained.

[0081] When the vehicle interior is cooled to a certain extent due tothe above maximum displacement operation of the compressor, the controldevice 68 reduces the duty ratio that is commanded to the drivingcircuit 68 a from the maximum. Accordingly, the first control valve CV1opens the supply passage 29 so that the pressure Pdk in the passage 82exceeds the suction pressure Ps in the valve chamber 77. Thus, thecondition expression (2) is satisfied, so that the spool 76 movesagainst the urging force f of the spring 85 in the direction to reducethe valve opening of the end valve portion 76 a and the first peripheralvalve portion 76 b of the first valve portion from the fully-openedstate as shown in FIG. 3.

[0082] In the second control valve CV2, in a state that the end valveportion 76 a and the first peripheral valve portion 76 b of the firstvalve portion of the spool 76 decreases the opening of the first bleedpassage 27 from the fully-opened state, the second valve portion 86 ofthe spool 76 opens the division of the back pressure chamber 78 and thepassage 82. Therefore, condition expression (3) for decreasing theopening of the first bleed passage 27 in the second control valve CV2 ina state that the first bleed passage 27 is opened but is not fullyopened is expressed as follows:

(Pdk−Ps)·SA>f  (3)

[0083] The condition expression (3) is effective due to the relation“SA>SB” as long as the urging force f of the spring 85 is fixed, even ifthe pressure difference “Pdk−Ps” between the pressure Pdk in the passage82 and the pressure Ps in the valve chamber 77 is smaller than theminimum value that satisfies the condition expression (2). Therefore,the spool 76 which has been distanced from the fully-opened state of thefirst bleed passage 27 by the formation of the condition expression (2)is moved in the direction to reduce the opening of the first bleedpassage 27 without stopping on the way by the formation of the conditionexpression (3). Since the urging force of the spring 85 is relativelysmall, the spool 76 which has been distanced from the fully-opened stateof the first bleed passage 27 is immediately moved to the closed stateof the first bleed passage 27.

[0084] Thus, the crank pressure Pc is immediately raised by opening thesupply passage 29 of the first control valve CV1 and closing the firstbleed passage 27 of the second control valve CV2. Consequently, thecompressor decreases the inclination angle of the swash plate 18 therebyto decrease the displacement of the compressor.

[0085] An amount of the compressed refrigerant gas that leaks from thedischarge chamber 22 to the crank chamber 15 further to the suctionchamber 21 is reduced to the amount of compressed refrigerant gas whichleaks only through the second bleed passage 28 by closing the firstbleed passage 27 in the second control valve CV2, so that a decrease inthe efficiency of the compressor is prevented. Furthermore, although therefrigerant circulation circuit in the present preferred embodiment isformed such that the refrigerant circulation stops by operating thecompressor at the minimum displacement (so called an off operation ofthe clutchless compressor), the off operation of the compressor isensured by closing the first bleed passage 27 in the second controlvalve CV2.

[0086] The present embodiment provides the following advantageouseffects.

[0087] (1) If the performance of the first control valve CV1deteriorates due to its aged deterioration, the first control valve CV1leaks the refrigerant gas even when the first control valve CV1 isoperated on the maximum duty ratio. When the first control valve CV1leaks the refrigerant gas, the pressure Pdk in the passage 82 is raisedand the spool is urged in the direction to reduce the opening of thefirst bleed passage 27 in accordance with the pressure Pdk.

[0088] However, the spool 76 of the second control valve CV2 provideswith the second valve portion 86 which blocks the opening 82 a of thepassage 82 in the back pressure chamber 78 in a state that the secondcontrol valve CV2 fully opens the first bleed passage 27. Therefore, inthe back surface 80 of the spool 76, referring to the conditionexpression (2), the pressure Pdk in the passage 82 is applied only tothe second valve portion 86, but is not applied to the back surface 80other than the second valve portion 86. Thus, in the first control valveCV1 in a state that the supply passage 29 is blocked, even if leakage ofthe refrigerant gas which is caused by the performance deterioration ofthe first control valve CV1 generates, the fully-opened state of thefirst bleed passage 27 is maintained even by the spring having smallurging force f, such that mechanical error of the second control valveCV2 is prevented. Consequently, the maximum inclination angle of theswash plate 18, that is, the maximum displacement operation (100%displacement operation) of the compressor is maintained.

[0089] If the spring 85 whose urging force is relatively small isadopted, the second control valve CV2 can set the first bleed passage 27at the minimum opening without increasing the pressure Pdk in the backpressure chamber 78 by widely opening the supply passage 29 in the firstcontrol valve CV1. Therefore, in a state that the first control valveCV1 opens the supply passage 29, the period in which the second controlvalve CV2 sets the first bleed passage 27 at the opening other than theclosed state is not increased. Thus, decrease in the efficiency of thecompressor is prevented.

[0090] (2) The second valve portion 86 of the second control valve CV2is shaped in a protruding shape and a taper shape so as to enter thepassage 82. Therefore, the opening 82 a of the passage 82 is closed bythe second valve portion 86.

[0091] (3) The back pressure chamber 78 of the second control valve CV2and the passage 82 for introducing the refrigerant gas from thedischarge chamber 22 to the back pressure chamber 78 form a part of thesupply passage 29. That is, in a state that the first control valve CV1closes the supply passage 29, the second valve portion 86 of the secondcontrol valve CV2 closes the supply passage 29 on the downstream side ofthe first control valve CV1. Therefore, in this state, even if therefrigerant gas leaks by the performance deterioration of the firstcontrol valve CV1, the leaked refrigerant gas is not supplied into thecrank chamber 15. Thus, the maximum inclination angle of the swash plate18, that is, the maximum displacement operation of the compressor ismaintained.

[0092] (4) The second control valve CV2 opens and closes the supplypassage 29 at a plurality of places. In the present preferredembodiment, the second control valve CV2 opens and closes the supplypassage 29 at two places of the second peripheral valve portion 76 c andthe second valve portion 86. Therefore, the second control valve CV2surely closes the supply passage 29 thereby further effectivelypreventing the refrigerant gas that leaks from the first control valveCV1 from being supplied into the crank chamber 15.

[0093] (5) The second valve portion 86 is made of resilient material.Therefore, the opening 82 a of the passage 82 is surely closed by thesecond valve portion 86 in response to the resilient deformation of thesecond valve portion 86.

[0094] (6) The first valve portion of the second control valve CV2 opensand closes the first bleed passage 27 at a plurality of places. In thepresent preferred embodiment, the first valve portion of the secondcontrol valve CV2 opens and closes the first bleed passage 27 at twoplaces of the end valve portion 76 a and the first peripheral valveportion 76 b. Therefore, the second control valve CV2 surely closes thefirst bleed passage 27 thereby further effectively preventing thedecrease in the efficiency of the compressor.

[0095] The present invention is not limited to the above-describedembodiment, but is modified as follows.

[0096] In the above-preferred embodiment, the second control valve CV2is arranged on the supply passage 29. In an alternative embodiment tothe above embodiment, as shown in FIG. 5, the second gap-hole 72 b ofthe second control valve CV2 is eliminated and the passage 83 directlycommunicates with the crank chamber 15. In addition, a branch passage 90is branched off the passage 83 and communicates with the passage 82 ofthe second control valve CV2. In this case, the passage 75 is exclusivefor the first bleed passage 27.

[0097] In an alternative embodiment to the above embodiment, the aspectof FIG. 5 is partially modified. The minimum opening of the first valveportion 76 a and 76 b is set to a value that is not zero by grooving thefirst valve portion 76 a and 76 b of the second control valve CV2 suchthat the first bleed passage 27 is continuously opened. The second bleedpassage 28 may be eliminated. In this case, the passages of thedisplacement control mechanism are simply formed.

[0098] In an alternative embodiment to the above embodiment, the aspectof FIG. 5 is partially modified. As shown in FIG. 6, positions at whichthe passage 75 and the passage 81 communicate with the second controlvalve CV2 are replaced by each other. In addition, a fixed throttle 83 ais formed on the passage 83. In this case, if the first bleed passage 27is continuously opened by setting the minimum opening of the first valveportion 76 a and 76 b at a value that is not zero, and further if thesecond bleed passage 28 is eliminated, the second valve portion 86 ofthe preferred embodiment of the present invention can be applied to thestructure similar to the prior art control valve which is shown in FIG.8.

[0099] In the above-described embodiments, the second valve portion 86of the second control valve CV2 is shaped in a protruding shape on theback surface 80 of the spool 76. In alternative embodiments to the aboveembodiments, the second valve portion 86 is eliminated from theabove-described embodiments. Instead, the back surface 80 may beregarded as a flat second valve portion by adhering resilient coat suchas rubber coat and resin coat on the back surface 80 of the spool 76. Ina technique other than adhering resilient coat on the back surface 80 ofthe spool 76 such that the back surface 80 of the spool 76 serves as asecond valve portion, it is proposed that the back surface 80 and theend surface 73 a of the fitting portion 73 are polished in highaccuracy.

[0100] In the above-described embodiments, the second control valve CV2opens and closes the supply passage 29 at a plurality of places (at twoplaces of the second peripheral valve portion 76 c and the second valveportion 86). In alternative embodiments to the above embodiments, thesecond control valve CV2 opens and closes the supply passage 29 at asingular place, or at the second valve portion 86.

[0101] In the above-described embodiments, the first valve portion 76 aand 76 b of the second control valve CV2 opens and closes the firstbleed passage 27 at a plurality of places (at two places of the endvalve portion 76 a and the first peripheral valve portion 76 b). Inalternative embodiments to the above embodiments, the first valveportion of the second control valve CV2 opens and closes the first bleedpassage 27 at a singular place such as the end valve portion 76 a or thefirst peripheral valve portion 76 b.

[0102] In the above-described embodiments, the spool 76 (a tubular body)is adopted as a valve body of the second control valve CV2. Inalternative embodiments to the above embodiments, a spherical body maybe adopted as the valve body. In this case, a hemispherical part of thespherical body on the side of the valve chamber 77 forms the first valveportion while the rest hemispherical part of the spherical body on theside of the back pressure chamber 78 forms the back surface and thesecond valve portion.

[0103] In the above-described embodiments, the spring 85 is a coilspring. In the present invention, however, the spring is not limited tothe coil spring. Other type of springs such as plate spring and torsionbar may be adopted.

[0104] In the above-described embodiments, the first control valve CV1varies the displacement of the compressor such that the pressuredifference (PdH−PdL) between the pressures on opposite sides of thethrottle 36 a is maintained at a predetermined target value (setpressure difference). Also, in the first control valve CV1, the setpressure difference is varied by external electric control. Inalternative embodiments to the above embodiments, the first controlvalve CV1 is operated such that the pressure in the suction pressureregion is maintained at a predetermined target value (set suctionpressure) while the set suction pressure is varied by external electriccontrol. In this case, the first control valve CV1 is so-called acontrol valve of variable set suction pressure type.

[0105] In the above-described embodiments, pressure sensing mechanismsuch as the pressure sensing chamber 48 and the bellows 50 may beeliminated from the first control valve CV1, and the first control valveCV1 may be varied to a simple electromagnetic valve.

[0106] In the above-described embodiments, the solenoid 60 may beeliminated from the first control valve CV1, and the first control valveCV1 may be varied to a simple pressure sensing valve which does notprovide with external control function.

[0107] The present invention may be applied to a displacement controldevice for a variable displacement type compressor of a wobble type.

[0108] Therefore, the present examples and embodiments are to beconsidered as illustrative and not restrictive and the invention is notto be limited to the details given herein but may be modified within thescope of the appended claims.

What is claimed is:
 1. A displacement control mechanism for controllingdisplacement of a variable displacement type compressor that forms arefrigerant circulation circuit for an air conditioning apparatus, thedisplacement being decreased as a pressure in a crank chamber riseswhile being increased as the pressure in the crank chamber falls, therefrigerant circulation circuit having a suction pressure region and adischarge pressure region, the displacement control mechanismcomprising: a bleed passage interconnecting the crank chamber with thesuction pressure region; a supply passage interconnecting the crankchamber with the discharge pressure region; a first control valvelocated on the supply passage for adjusting an opening of the supplypassage at a position of valve opening adjustment; a second controlvalve comprising; a back pressure chamber to which a pressure on adownstream side of the position of valve opening adjustment of the firstcontrol valve in the supply passage is introduced through anintroduction passage; a valve chamber forming a part of the bleedpassage; a valve body having a first valve portion located in the valvechamber and a back surface located in the back pressure chamber, thefirst valve portion decreasing an opening of the bleed passage as apressure in the back pressure chamber which is applied to the backsurface rises; a spring for urging the valve body so that the firstvalve portion increases the opening of the bleed passage; and a secondvalve portion provided with the back surface of the valve body, thesecond valve portion closing an opening of the introduction passage inthe back pressure chamber when the first valve portion maximizes theopening of the bleed passage.
 2. The displacement control mechanismaccording to claim 1, wherein the second valve portion is so shaped asto protrude and taper from the back surface toward the opening of theintroduction passage, the second valve portion closing the opening ofthe introduction passage by entering the introduction passage.
 3. Thedisplacement control mechanism according to claim 1, wherein theintroduction passage and the back pressure chamber form a part of thesupply passage.
 4. The displacement control mechanism according to claim3, wherein the second control valve opens and closes the supply passageat a plurality of places.
 5. The displacement control mechanismaccording to claim 1, wherein the second valve portion is made ofresilient material.
 6. The displacement control mechanism according toclaim 1, wherein the first valve portion of the second control valveopens and closes the bleed passage at a plurality of places.
 7. Thedisplacement control mechanism according to claim 1, wherein thevariable displacement type compressor is of a clutchless type, thevariable displacement type compressor of clutchless type is such avariable displacement type compressor that continues to rotate a driveshaft in a state that a minimum inclination angle of a cam plate ismaintained such that a refrigerant is not substantially flowed into anexternal refrigerant circuit while a refrigeration cycle stops.